iproute2: bridge: Close file with bridge monitor file

The `bridge monitor file FILENAME' reads dumped netlink messages from
a file. But it forgot to close the file after using it. This patch
fixes it.
Signed-off-by: Petr Písař <ppisar@redhat.com>

bridge/monitor.c

@@ -132,12 +132,15 @@ int do_monitor(int argc, char **argv)
 
 	if (file) {
 		FILE *fp;
+		int err;
 		fp = fopen(file, "r");
 		if (fp == NULL) {
 			perror("Cannot fopen");
 			exit(-1);
 		}
-		return rtnl_from_file(fp, accept_msg, stdout);
+		err = rtnl_from_file(fp, accept_msg, stdout);
+		fclose(fp);
+		return err;
 	}
 
 	if (rtnl_open(&rth, groups) < 0)